Method for power control of a fuel cell system in a vehicle

Abstract

A method for power control of a fuel cell system in a vehicle is disclosed. The requested fuel cell system power by the vehicle is converted into a power request made of the fuel cell by an expected power of auxiliary drives of the fuel cell system at the requested fuel cell system power being added to the requested fuel cell system power. A media supply of the fuel cell which corresponds to the power request made of the fuel cell is requested. The electrical loading of the fuel cell with current is performed in accordance with a model of the cathode dynamics such that a control variable of the control operation is matched to the media dynamics, and the power release is performed such that the fuel cell is loaded only when the adequate media supply is ensured.

The invention claimed is: 
     
       1. A method for power control of a fuel cell system in a vehicle, comprising the steps of:
 providing fuel cell system power (PFCS) starting from a requested fuel cell system power (PVEH,soll) by the vehicle; 
 wherein the requested fuel cell system power (PVEH,soll) is converted into a power request (PFC,soll) made of a fuel cell by adding an expected power (PAUX,soll) of auxiliary drives of the fuel cell system at the requested fuel cell system power (PVEH,soll) to the requested fuel cell system power (PVEH,soll); 
 wherein a media supply of the fuel cell which corresponds to the power request (PFC,soll) made of the fuel cell is requested; 
 wherein electrical loading of the fuel cell with current (IFC) is performed such that a power required from the fuel cell is always only a power which can be supplied by the fuel cell on a basis of dynamics of the media supply to the fuel cell as predicted by a model; 
 and wherein the expected power (PAUX,soll) of the auxiliary drives of the fuel cell system is predicted by a characteristic field as a function of variables of power, pressure and temperature. 
 
     
     
       2. The method according to  claim 1 , wherein the characteristic field is re-adapted in a static mode of the fuel cell system. 
     
     
       3. The method according to  claim 1 , wherein, with respect to the request for the media supply, pressure and either mass flow or volume flow of a respective medium are predetermined. 
     
     
       4. The method according to  claim 3 , wherein the request for the media supply takes place on a basis of a current setpoint (IFC,soll) of the power request (PFC,soll) made of the fuel cell. 
     
     
       5. The method according to  claim 4 , wherein the current setpoint (IFC,soll) is determined by a polarization curve of the fuel cell from the power request (PFC,soll) made of the fuel cell. 
     
     
       6. The method according to  claim 5 , wherein the polarization curve is approximated linearly under at least one predetermined condition. 
     
     
       7. The method according to  claim 5 , wherein the current setpoint (IFC,soll) transmitted to the media supply and/or a setpoint for a current load of the fuel cell are limited such that a permitted operating range (OR) in a diagram of the polarization curve of the fuel cell, starting from a point of maximum power (PFC,max), is in a direction of higher current intensities or in a direction of lower current intensities (IFC). 
     
     
       8. The method according to  claim 4 , wherein air mass flow to a cathode is measured and the current setpoint (IFC,soll) is limited on a basis of the measured air mass flow. 
     
     
       9. The method according to  claim 4 , wherein the current setpoint (IFC,soll) passed to the media supply is adapted to a current value (IFC) drawn from the fuel cell if the vehicle does not take off the current or does not take off the current completely.